There is known a color system where an array or series of different color imaging stations are aligned above an endless belt. Each station contains an upper positioned raster output scanner (ROS), and below the ROS an imaging station comprising a photoreceptor drum, development station, and cleaning station. The ROS emits an electronic beam (laser) which impinges on the rotating photoconductive drum, thereby causing that location on the drum to undergo a change in electrical charge. As the drum continues to rotate past the development station, toner particles of a color which is unique to that imaging station will attach to the drum at the location charged by the ROS. This colored image is then transferred to an intermediate transfer belt that is passing by, and in contact with, the photoreceptor drum. As the intermediate belt passes by the different imaging stations (each usually containing a different color) it picks up subsequent color layers to create a complete color image which is then transferred to media.
Each colored beam must be in substantial registration with the other beams deposited on the belt for a final color copy. This registration is monitored by a sensor(s) to ensure proper alignment. If any color needs to be re-aligned or skewed, the ROS or imaging station is moved accordingly. In one embodiment there are also two sensors (Mark On Belt, or MOB sensors) that are fixed in position to a point on the machine frame, such that the colored images pass within view of these sensors. These sensors serve to detect the misregistration or misalignment between colors. The actuation of the deskew portion of the correction is performed via either a ROS mechanism or with an imaging station deskew mechanism, as in this invention. Each ROS unit and imaging station has its own motor so that they could independently be skewed for image alignment. This type of color system having an array of ROS units is generally described in U.S. Pat. No. 6,418,286 and is incorporated by reference into this disclosure.
Also, in U.S. application Ser. Nos. 12/053,704 and 12/053,753 structures and systems for deskewing the movable ROS unit are disclosed. The present invention involves a stationary ROS unit and a movable imaging station below said ROS (Raster Output Scanner). The disclosures of Ser. Nos. 12/053,704 and 12/053,753 are incorporated herein by reference.
As noted above, the color image deposited on the drum is subsequently deposited onto the belt. As the drum continues to rotate, it passes through the development station with a latent image which causes toner to stick to the drum where the electrical discharging (by the ROS) has taken place. The drum further rotates until the image is in contact with this intermediate transfer belt where the image is transferred from the drum to the belt. Each of the six or plurality of imaging stations deposits its own color and subsequently movement of the belt is moved past each of the imaging stations and allows each of the color separations to be deposited in turn. Thus, when the colors are out of alignment as indicated by sensors, the image needs to be skewed as does the image beam. By placing registration images side by side on the intermediate belt, the MOB sensors will indicate (to a controller or to a motor adjacent each unit), how much each imaging station needs to be skewed to provide the optimum color-to-color registration deposited on the belt by the six or several ROS-imaging station units.
When these units in the prior art are not robust to vibration sources within the imaging system, they cause “banding”. These prior art units are susceptible to vertical vibration which generally causes imprecise image deposition. By “banding” is meant a series of dark and light image lines causing image quality defects or color variations. The present invention involves an improved ROS fixed mounting and a movable imaging station skew adjustment mechanism.